1. Field of the Invention
This invention relates generally to pallets on which articles are stacked or assembled for volume handling by fork-lift trucks to enable handling and shipment of the articles at minimal labor and handling costs. More specifically, the present invention relates to plastic pallets which are constructed from virgin or reclaimed or recycled plastic materials and which have wear and damage resistance exceeding that of conventional pallets constructed of wood. Even more specifically, the present invention concerns plastic pallets composed of virgin, reclaimed or recycled plastic materials and which incorporate strategically located reinforcement to provide for wear and damage resistance far exceeding that of conventional wood or plastic pallets.
2. Description of the Prior Art
Fork-lift pallets have been in wide use for many years to minimize the cost of products or articles that can be stacked or otherwise secured on them to thus enable large volumes or products or articles to be handled simultaneously and to be handled in mechanized fashion so as to minimize labor costs. Historically, fork-lift pallets have been constructed of wood, having a plurality of parallel stringers on which are nailed or otherwise secured one or more structural members defining a pallet platform. The pallet platform can be composed of multiple wood strips or unitary wood panels, such as plywood panels, to provide a generally planar support surface on which the goods or articles are appropriately arranged or stacked. The parallel stringers raise the product support platform above a floor surface and thereby permit the forks of a fork-lift truck to be insurted within spaces defined between the stringers. This enables a fork-lift truck to lift and move the pallet with all of its articles as a unit or package. Typically, the pallet will remain with the products or articles until such time as the articles are removed from the pallet for further handling, for use or for distribution.
Even though pallets are typically of low cost, nevertheless they are sufficiently costly that they are used many times for shipment of products before they become sufficiently worn or damaged that replacement is necessary. Although wood has historically been a low cost commodity, thus enabling pallets to be manufactured of wood at low cost, of late, the cost of wood for products such as pallets has significantly increased, thus causing pallet manufacturers to seek other sources for materials. Pallets have been constructed of extruded or formed metal such as steel or aluminum. Pallets have also been constructed of molded or extruded plastic materials, including virgin plastic material or plastic material that has been recycled or reclaimed from waste.
A significant volume of waste plastic material is, at the present time, disposed of in landfills and is seen as a viable source of raw plastic material that can be prepared and utilized for the manufacture of simple products such as pallets, structural materials for buildings, railroad ties, etc. Use of these materials, which would otherwise constitute waste and require this disposition at significant expense, is seen as significant from the standpoint of industrial and government controlled economics. Moreover, products manufactured from plastic material whether virgin or reclaimed plastic material, have been found to have considerable wear resistance as well as resistance to damage by water or other environmental materials. Thus, plastic material, especially reclaimed plastic material, because of its abundance and its detriment to the environment and because of the present day cost of its handling and disposal, is seen as a viable source of material for pallet manufacture.
Pallets that are constructed of plastic material, whether virgin or reclaimed plastic material, have been found to have problems which the present invention effectively addresses. Plastic pallets manufactured at the present time are made by either injection molding or made by screwing, nailing or otherwise fastening plastic profiles in somewhat similar fashion to the manufacture of wood pallets. In both the injection moulding or assembling of plastic profiles, the costs are much higher than the cost of their wood counterparts, therefore making plastic pallets somewhat uneconomical as compared to pallets composed of conventional wood structure. Most of the plastic pallets that are currently produced are not "rackable" due to the plastic bending when located in a rack and under load. This pallet bending or yielding phenomenon is known as "creep" where the plastic under load will bend, thereby allowing the pallet to dislodge from a rack on which it rests since the pallet is supported on the rack only by resting on its edges. Accordingly, it is considered desirable to provide a novel pallet construction wherein the pallet or it components are constructed largely of molded or extruded plastic material and yet are structurally reinforced by internal structural elements that are preferably composed of metal, but which can be composed of wood or plastic materials when sufficient strength is afforded thereby.